1. Field of the Invention
This invention relates generally to medical devices, such as catheters, and particularly to enteral feeding catheters.
2. Description of the Related Art
Feeding-decompression catheters must reside within the gastrointestinal (G-I) tract of patients for prolonged periods. A catheter may be delivered by direct penetration through the abdominal and gastrointestinal walls. Some directly placed catheters may then be directed to traverse the normal G-I channels to reach a more distal duodenal or jejunal feeding and/or aspiration site.
Alternatively, the catheter may be introduced indirectly and less traumatically into the body through a natural opening (e.g., nasal passage), to then traverse the natural G-I channels to the gastric or intestinal feeding and/or aspiration site. As the catheter encounters sharp bends and makes prolonged contact, it may irritate sensitive tissue. The size of the nasal passage and ever increasing discomfort limit the maximum outside diameter (O.D.) of a useful nasal catheter to about 6.7 mm, or about 20 Fr (French) units, wherein 3 Fr units=1 mm.
Some catheters are single lumen catheters and others are dual lumen devices which include feeding and aspirating tubes. Such single and dual lumen catheters are disclosed in U.S. Pat. Nos. 3,618,613, 4,543,089, 4,642,092, 4,705,511, 4,806,182, 5,334,169, 5,520,662, 5,599,325, 5,676,659, 5,807,311, 5,947,940, 6,508,804, 6,659,974, 6,881,211, 6,921,396 and 6,949,092, the contents of which are incorporated entirely herein by reference.
The O.D. of all feeding devices must be minimized to reduce patient trauma and discomfort. The catheter must provide necessary clearances to accommodate feeding inflow and/or aspirate outflow, while also minimizing the likelihood of blockage.
The internal diameter (I.D.) of a feeding channel required to accommodate an adequate flow rate by gravity feed or by pump can be met easily. However, the adequacy of aspiration flow is less certain. The volume of aspirate to be removed fluctuates, and often exceeds many-fold the rate of feeding. Excess digestive juices and swallowed air that escape removal may be propelled downstream, to accumulate and cause distention. Further, the aspiration channel is at greater risk for occlusion by the particulates and mucus encountered in the gastrointestinal fluids. The I.D. of the aspiration channel, especially, must be maximized.
The enteral feeding catheter is used to provide patients with nourishment, utilizing the propulsion and absorption functions of the gastrointestinal tract. Adequate food nourishes the patients, accelerates healing, aids infection resistance, and decreases recovery time. However, G-I motility of hospitalized patients is characteristically impaired by disease and/or trauma, including the trauma incident to surgery.
An aspirating tube is positioned proximal to the feeding site to reduce abdominal distention, which occurs when air and excess fluids accumulate. The aim of this aspiration is to intercept all swallowed air, and also remove any inflowing liquid that exceeds the patient's capacity for outflow via peristalsis from the feeding site. The outer layer of the aspirating catheter must allow for inflow of fluid, between the coils of the spring band. If the inner skeleton (the spiral spring band) was overlaid with a layer of continuous plastic, multiple holes will have to be provided by punching, laser drilling, etc.
Abdominal distention exerts its harmful effects in several ways. It reduces the ability of the patient to adequately breathe deeply, cough and clear secretions, predisposing to pneumonia. It causes extreme discomfort and limits mobility. It interferes with nutrient absorption. The resulting undernourishment slows the healing process, reduces the patient's optimum resistance to infection, and increases the recovery time.
When a catheter is inserted via the nose, it bends to conform to the nasal passage, esophagus, etc. The bent catheter may kink, causing partial or total occlusion. This is prevented in standard catheters by increasing the thickness of the flexible wall.
One example of such a current feeding tube from CR Bard, Inc. is a gastrostomy catheter for direct placement into the stomach. It has an I.D. of 6 mm and an O.D. of 9.3 mm, or 28 Fr units. The wall thickness of 1.67 mm (5 Fr units) is designed to prevent kinking. A 28 Fr catheter is too large and uncomfortable to insert transnasally in a patient. The nasal catheters in current use are necessarily more slender, and therefore have lumens with compromised functionality.
Therefore, it is an object of the present invention to provide a catheter with an ultra-thin wall that is less likely to experience kinking in response to being bent.